This invention relates to a functional evaluation device for evaluating an artificial device, such as an artificial joint.
Various kinds of artificial devices have been recently manufactured and put into practical use. As one of the artificial devices, an artificial joint is proposed which comprises a joint element of metal, ceramics, or plastics The joint element may be a coated metallic element coated with ceramics or the like. An artificial hip joint will be exemplified as such an artificial joint hereinafter. The artificial hip joint is buried between two pieces of bones in a living body, such as human body, to join two pieces of bones together and to thereby restore normal activity of the living body. In this case, the artificial hip joint must be buried in the living body so as not to harm a motion of a patient as far as possible.
To this end, such an artificial hip joint is fixed at both ends thereof to the pelvis and the femur without any cement. The artificial hip joint resorts to ingrowth or regeneration of the bones adjacent to the artificial hip joint. Such ingrowth of the bones brings about cohesion between the artificial hip joint and the bones and is effective to firmly fix the artificial hip joint to the bones.
In practical use, it happens that the artificial hip joint is excessively sunk into a femur of a patient, which may be called "sinking" hereinafter. In addition, the artificial hip joint often becomes loose due to a crevice between the femur and the artificial hip joint, which may be referred to as "loosening." Such sinking and loosening weaken the cohesion between the artificial hip joint and the bones and give rise to functional degradation of the artificial hip joint. On occurrence of such functional degradation, the artificial hip joint must be superseded by a new one by a surgical operation. The surgical operation is painful for the patient physically and economically and thus, it would be desirable to find a way to avoid the need for such an operation.
It has been found out that the cohesion between the bones and the artificial hip joint can be recuperated without a surgical operation by a rest cure even after occurrence of the functional degradation, if the sinking and the loosening are discovered in their early stages. Therefore, it is important to early detect the functional degradation.
At present, such detection of sinking and loosening of the artificial hip joint must depend on consciousness of the patient, X-ray inspection, and motor function inspection. This means that the functional degradation of the artificial hip joint is detected and evaluated by relying on subjectivity of a patient and/or a doctor. However, such detection of the sinking and the loosening is not always easy for the patient and the doctor. Therefore, discovery of such sinking or loosening is liable to be too late to recuperate the sinking or the loosening by a rest cure. Under the circumstances, it is preferable that the sinking and loosening can be detected and evaluated with objectivity.